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Shoji T.,Toyota Motor Corporation | Katsumata S.,Sony Corporation | Nakaura S.,Sasebo College of Technology | Sampei M.,Tokyo Institute of Technology
IEEE Transactions on Control Systems Technology | Year: 2013

This brief describes a control strategy for the throwing motion of an underactuated two-link planar robot called the Pendubot. The springed Pendubot is built based on the concept of unstable zero dynamics, and our investigation uses it as a dynamic model of superior limbs to imitate human throwing motion. In the proposed control strategy, the zero dynamics is intentionally destabilized when a ball held by the end-effector is constrained on a geometric path in a vertical plane, using output zeroing control for the deviation between the ball and geometric path. The unstable zero dynamics drives the ball along the geometric path to achieve fast and accurate throw in a desired direction. The unstable zero dynamics is analytically derived to guarantee the dynamic acceleration of the ball along the geometric path. Numerical simulations and experimental results confirm the effectiveness of the proposed control strategy. © 1993-2012 IEEE.


Kinoshita T.,Kyoto University | Watanabe Y.,Kyushu University | Nakao M.T.,Sasebo College of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

This paper presents a new numerical method to obtain the rigorous upper bounds of inverse linear elliptic operators. The invertibility of a linearized operator and its norm estimates give important informations when analyzing the nonlinear elliptic partial differential equations (PDEs). The computational costs depend on the concerned elliptic problems as well as the approximation properties of used finite element subspaces, e.g., mesh size or so. We show the proposed new estimate is effective for an intermediate mesh size. © Springer International Publishing Switzerland 2016.


Nakao M.T.,Sasebo College of Technology | Kinoshita T.,Kyoto University | Kimura T.,Sasebo College of Technology
Computing | Year: 2012

We present numerically verified a posteriori estimates of the norms of inverse operators for linear parabolic differential equations. In case that the corresponding elliptic operator is not coercive, existing methods for a priori estimates of the inverse operators are not accurate and, usually, exponentially increase in time variable. We propose a new technique for obtaining the estimates of the inverse operator by using the finite dimensional approximation and error estimates. It enables us to obtain very sharp bounds compared with a priori estimates. We will give some numerical examples which confirm the actual effectiveness of our method. © 2011 Springer-Verlag.


Tanaka M.,Kyushu University | Higashida K.,Kyushu University | Higashida K.,Sasebo College of Technology
Philosophical Magazine | Year: 2016

The effects of severe plastic deformation on the thermal activation of dislocation gliding in ultralow-carbon steel at low temperatures were investigated. This was done by measuring the temperature dependences of the effective stress, activation volume and activation energy. It was found that the values of all these parameters were lower than those for coarse-grained specimens at low temperatures. In coarse-grained materials, the activation energy should increase with a decrease in the effective stress. This phenomenon, which seemed counterintuitive initially, could be physically interpreted on the basis of the fluctuation in the athermal stress. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.


Nakamura K.,Tokyo Institute of Technology | Nakaura S.,Sasebo College of Technology | Sampei M.,Tokyo Institute of Technology
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2010

This paper investigates the running control problem for the 7-link, 6-actuator planar bipedal robot including ankle joints. The control strategy is based on the "synchronization structure" with the angular momentum of the pivot point. The synchronization not only follows the simplified joint angle dynamics of human running but also generates the uniform running speed from wide range of initial speed, which claims that the controller is robust for the error of initial speed. Moreover, it successfully verifies the acceleration of running speed from 0.1[m/s], which is almost zero speed, to a uniform running speed "without" switching controllers. Finally, the controller is applied for the running on an uneven terrain, and it successfully achieves running with the maximum slope angle 6[deg], which is highly steep terrain in the real situation. ©2010 IEEE.


Takeichi T.,Toyohashi University of Technology | Kano T.,Toyohashi University of Technology | Agag T.,Toyohashi University of Technology | Kawauchi T.,Toyohashi University of Technology | Furukawa N.,Sasebo College of Technology
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2010

High-molecular-weight polybenzoxazine prepolymers containing polydimethylsiloane unit in the main-chain have been synthesized from α,ω-bis(aminopropyl)polydimethylsiloxane (PDMS) (molecular weight = 248, 850, and 1622) and bisphenol-A with formaldehyde. Moreover, another type of prepolymers was prepared using methylenedianiline (MDA) as codiamine with PDMS. The weight average molecular weight of the obtained prepolymers was estimated from size exclusion chromatography to be in the range of 8000-11,000. The chemical structures of the prepolymers were investigated by 1H NMR and IR analyses. The prepolymers gave transparent free standing films by casting their dioxane solution. The prepolymer films after thermally cured up to 240 °C gave brown colored transparent and flexible polybenzoxazine films. Tensile test of the films revealed that the elongation at break increased with increasing the molecular weight of PDMS unit. Dynamic mechanical analysis of the thermosets showed that the T gs were as high as 238-270 °C. The thermosets also revealed high thermal stability as evidenced by the 5% weight loss temperatures in the range of 324-384 °C from thermogravimetic analysis. © 2010 Wiley Periodicals, Inc.


Kaneda Y.,Tokyo Institute of Technology | Sadahiro T.,Sasebo College of Technology | Yamakita M.,Tokyo Institute of Technology
Proceedings of the SICE Annual Conference | Year: 2011

Differentiator is widely used to calculate derivative of measured signal in many fields. To improve characteristics of frequency responses, a differentiator using Richardson extrapolation and fractional delay has been proposed. However, to implement fractional delay, some sort of high-order interpolator is needed, which causes many problems. In this paper, to resolve the problems caused by the high-order interpolator, a higher sampling rate system is implemented on FPGA, which acts like a system using fractional delay. A way to implement the proposed method on FPGA is described, and its effectiveness is verified by some experiments. © 2011 SICE.


Makita S.,Sasebo College of Technology | Nagata K.,Japan National Institute of Advanced Industrial Science and Technology
Advanced Robotics | Year: 2016

In partial caging, an object is partially constrained by robots and is able to escape from there. Although complete caging ensures the hand never releases the confined object, insufficient degrees of freedom of robots does not often satisfy the conditions for caging. Partial caging, however, can be accomplished even by robots having such mechanical restriction. We consider a case that an object moves in the semi-closed region formed by a planar robot hand with two fingers, as an example of partial caging in two-dimensional space. Then the parameters of fingers: joint angles interfere in the object motion to escape from the hand through the gap between the fingertips. Some simulation results show differences of difficulty of escaping according to arrangement of fingers, and factors interfering in the difficulty are analyzed. Additionally, we also evaluate ease of entering the hand through the gap and define an ability index of robot hand for partial caging with the above two evaluation scores. Then a high index score indicates that the hand assumed to be able to capture objects easily and confine it without any finger motion. It can be utilized for mechanical design and controlling strategies of robots in capturing objects. © 2016 Taylor & Francis and The Robotics Society of Japan


Makita S.,Sasebo College of Technology | Maeda Y.,Yokohama National University
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2013

Graspless manipulation is easily interfered by external disturbances because the manipulated object is not completely held by a robot hand and supported by an environment such as a floor. Thus it is important to ensure the manipulation is executed robustly against some disturbances. In our works, a rigid-body-based analysis of indeterminate contact forces for quasi-static graspless manipulation has been proposed, and also joint torque optimization for robotic hands. The joint torques of the robot is determined in consideration of some robustness of manipulation against disturbances, which include changes or estimation errors of friction. In the analysis of contact forces in quasi-statics, a kinematic constraint on static friction is considered to exclude infeasible sets of frictional force, with considering treatment of kinetic friction. Additionally, new objective functions for computing optimal joint torques in both static and quasi-static graspless manipulation are proposed. Some numerical samples of both applications are shown to verify our proposed methods. © 2013 IEEE.


Makita S.,Sasebo College of Technology | Nagata K.,Japan National Institute of Advanced Industrial Science and Technology
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2015

In caging, an object is geometrically confined by position-controlled robots and never escapes from the constraint. Caging has some advantages over conventional grasping, and its applications have been performed not only in 2D but also in 3D scenes with various actual robots. However, the conditions of complete caging are not always satisfied due to limited robot configuration. This paper studies partial caging, in which an object is incompletely confined by robots or obstacles and is able to escape from the constraint. As an example of partial caging, a circular object moving in the planar hand is considered. We investigate an effect of arrangement of its fingertips, which prevents the object from escaping outside through the gap between the fingertips. Some simulation results show differences of difficulty of escaping for the object according to width of the gap and angle of the fingers. In addition, ease of entering the hand through the gap of the fingers is also evaluated. From these two scores on partial caging, we define an ability index for the hand, which represents the hand can easily capture an object and confine it without any finger motion. © 2015 IEEE.

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